The long-term objective of the proposed research is the identification and molecular, genetic and biochemical characterization of microbial metabolic processes involved in oxidation-reduction reactions of phosphorus compounds. These reactions have been little studied and represent novel aspects of the biochemistry of this important element, which plays a central role in the metabolism of all living organisms. The production and consumption of reduced P compounds are known to occur in many organisms, including humans. The metabolism of these compounds has importance with respect to the natural roles of these compounds in the organisms where they are found, and with respect to the toxicity and environmental persistence of man-made reduced P compounds, which are widely used for industrial, agricultural and military purposes. Further, phosphorus is the limiting nutrient in many ecosystems. Redox reactions of phosphorus may play an important role in the bioavailability and global cycling of this required nutrient. To further our understanding of these processes we have isolated a number of microorganisms that possess novel biochemical pathways involving redox chemistry of P compounds. The experiments proposed here involve identification and characterization of these reactions at the genetic and biochemical levels. The specific goals of these experiments are: 1) purification and characterization by standard biochemical approaches of two novel enzymes involved in a P oxidation pathway in Pseudomonas stutzeri, 2) characterization of the functions and genetic regulation of the 14 genes (at least) involved in this P. stutzeri pathway using mutant analysis and transcriptional reporter gene studies, 3) molecular, genetic, and biochemical characterization of a novel pathway for oxidation of phosphite by Escherichia coli, 4) molecular genetic characterization of a novel pathway for anaerobic hypophosphite oxidation by a new bacterial isolate, and 5) isolation and characterization of organisms that possess other novel metabolic pathways involving P redox reactions.